Field
Exemplary embodiments relate to a touch sensor and touch panel having the same.
Discussion of the Background
Display devices, such as a liquid crystal display (LCD), an organic light emitting display device, and an electrophoretic display, include an electric field generating electrode and an electro-optical active layer. For example, an organic light emitting display device includes an organic light emitting layer as an electro-optical active layer. An electric field generating device may be connected to a switching element, such as a thin film transistor to receive a data signal, and an electro-optical active layer may converts, such a data signal into an optical signal to display an image.
The use of heavy and easily damaged glass substrates in a display panel of a display device limits the portability of a display. Recently, light, flexible, and impact resistant plastic substrates have been actively developed for flexible display devices.
Display devices may include a touch sensing function allowing for a user to interact with the display in addition to the function to display an image. The touch sensing function enables a display device to obtain contact information (i.e., input) from a user. For example, the touch sensing display may sense when an object approaches or comes into contact with its screen. The touch sensing display may determine a contact position of the object by sensing a change in pressure, electric charge, light, and the like, applied to the screen when a user brings his or her finger or a touch pen into contact with a screen or places the same in proximity to the screen to write down characters or draw a picture. The display device may receive an image signal on the basis of such contact information and display an image.
The touch sensing function may be realized through a touch sensor. The touch sensor may be classified according to various schemes, such as a resistive type touch sensor, a capacitive type touch sensor, an electromagnetic (EM) type sensor, and an optical type sensor
The capacitive type touch sensor includes a plurality of touch electrodes capable of transmitting a sensing signal. A touch electrode may form a sensing capacitor together with another touch electrode (mutual-capacitor type) or form a sensing capacitor together with an external object (self-capacitor type). When a conductor, such as a finger, approaches a touch sensor or comes into contact with the touch sensor, capacitance of the sensing capacitor or a charged quantity of electric charge is changed to recognize whether a contact has been made and a contact position, or the like.
A plurality of touch electrodes are disposed in a touch sensing area in which a contact may be sensed, and may be connected to a plurality of signal transmission lines that transmit a sensing signal. The signal transmission lines may be positioned in a non-sensing region near the touch sensing area. The signal transmission line may transmit a sensed input signal to a touch electrode or may transmit a sensing output signal of a touch electrode generated according to a touch to a sensing signal control unit.
The touch sensor may be installed in a display device (in-cell type) or directly formed on an outer surface of a display device (on-cell type). Alternatively, a separate touch sensor unit may be attached to a display device (add-on cell type). With a flexible display device, the touch sensor is generally formed on the display panel as a film or as a separate plate-type touch sensor unit attached on the display panel (add-on cell type).
A mutual capacitive type touch sensor may include an input touch electrode for receiving a sensing input signal and an output touch electrode for transmitting a sensing output signal. When this type of touch sensor is used, the signal lines connected to the input touch electrodes and the output touch electrodes are formed in the peripheral areas (non-sensing region) resulting in an increase in a width of the peripheral areas. The increase in a width of the peripheral areas may result in larger electronic circuitry and larger devices (e.g., mobile phones, tablets) or may limit the valuable space in electronic circuitry for other components.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.